A distributed control system (DCS) is commonly arranged to control operation of a geographically extensive industrial facility. In addition, it can include one or several superordinate automation servers and data storage units for performing higher level tasks in connection with the managing of the industrial facility, for example central monitoring and supervision as well as life cycle management of the industrial facility's components. The industrial facility can belong to different industry sectors, such as the discrete manufacturing industry, or the power generation industry, or the process industry such as the pharmaceutical, the chemical or the mineral and oil and gas industry. In other words, the industrial facility can for example be a power plant, a substation, a chemical plant or an automated factory.
The DCS commonly includes field devices located close to the actual production process of the industrial facility and, accordingly, being distributed across the industrial facility. Field devices can be those devices which interact directly with the production process, (e.g., actuators, sensors), as well as those devices which directly communicate with the actuators and sensors (e.g., local control devices and local I/O (input/output) modules). The communication is performed via fieldbuses. Further, the DCS includes network devices for enabling the network communication between the field devices and the superordinate automation servers and data storage units, wherein the network devices include switches, routers and gateways.
Because a DCS can include between several hundred to several thousand components which communicate with one another over an extensive communication network, involving multiple network protocols, a considerable effort can be required to ensure seamless and reliable engineering, configuring, securing, commissioning and maintaining of the DCS. Due to the sheer number of components, it is no longer possible to perform these tasks without the help of computerized tools.
An important step during the above tasks can be the analyzing of the interaction between the components of the DCS, wherein the analysis can be performed based on a computerized model of the infrastructure of the communication network or networks, or based on a computerized model of the functional behavior of controllers, actuators and sensors in connection with the physical behavior of the industrial facility.
For example, a computerized model of an automation system of an electric power system is described in “A reference model for control and automation systems in electric power” by Michael Berg and Jason Stamp, published by U.S. Department of Energy, Sandia National Laboratories, December 2005. The model is used for analyzing security issues in the automation system. It is created using object-role modeling, wherein not only single hardware or software components of the automation system, but also sub-systems, groups of data and even personnel can be modeled as objects. The objects can serve as references for features and properties which can be common across all instances of that object within the system. Relationships between the objects can be modeled as roles. The number of roles is not limited. The paper, for example, includes such roles as “monitored by”, “sampled by”, analyzed by”, “aggregates”, “calls” and “commanded by”. The model proposed in the paper covers several levels of the automation system, starting from the field devices over SCADA components (supervisory control and data acquisition) and the control center, up to so called oversight entities, such as regional transmission operators and business objectives. Nevertheless, the model focuses exclusively on functional aspects of the automation system, without taking into account any communication network infrastructure.
Another example for modeling an automation system is described in “Communication Network Modeling and Simulation for Wide Area Measurement Applications” by Yi Deng et al., Proceedings of the 2nd IEEE International Conference on Smart Grid Communications (Smart-GridComm), Brussels, Belgium, Oct. 17-20, 2011. Here, a simulation model of the communication network of a Wide Area Measurement System (WAMS) is presented which is used for evaluating various communication infrastructure choices. The WAMS network is modeled in OPNET software in a hierarchical way, corresponding to the actual protocol layer, the device layer and the network layer. The WAMS network is modeled by an undirected graph with nodes representing substations—in their capacity as participants of communication over the optical fiber network of the WAMS—as well as a centralized Super Phasor Data Concentrator which is used for processing data uploaded from the substations. Further, the routers of the ring shaped communication backbone network can be each represented by a node. The field equipment of the WAMS, namely Phasor Measurement Units (PMUs), relays and circuit breakers can be represented in OPNET by workstations and servers. In other words, they can be regarded purely under the aspect of their network communication functionality. Based on the WAMS network model, it is then possible to vary communication parameters, such as data bandwidth and communication protocol, and to compare their influence on the performance of the WAMS communication network.
However, with the existing tools, it is not yet possible to quickly analyze the potential impact which a change in a network communication device, such as a switch or router, can have on the interaction of field devices, such as the functionality of a specific control loop, and vice versa. In other words, the interdependency of DCS components belonging to different domains, for example the control domain versus the network communication domain versus the monitoring and supervisory domain, is not yet covered by any of the known computerized tools.